When a book sells in the huge numbers that EL James’s Fifty Shades of Grey is maintaining this summer, the world must surely be full of people who have enjoyed it and then told their friends.

Fans were certainly quick to defend Dan Brown’s The Da Vinci Code as it broke publishing records back in 2003, and Harry Potter addicts, both young and old, have been proud to wave a wand on behalf of JK Rowling’s bestsellers since 1997. But what makes the triumph of James’s book surprising is that a story involving such a succession of overtly kinky sex scenes can conquer the mainstream publishing market. After all, the plot is so singlemindedly titillating that it makes the unconventional “modern” relationships that leaven Stieg Larsson’s Millennium Trilogy read like Charlotte Brontë in comparison.

Last month the first novel in this series telling the story of Anastasia Steele and her obsessive love for a man with a predilection for bondage and domination became the fastest-selling paperback since records began and last week it also became the first ebook to sell more than one million copies. Yet its story pivots on the young heroine’s sexual submission to Christian Grey, a millionaire she scarcely knows, who promptly introduces her to his favourite fetishes, as well as to the contents of his “Red Room of Pain”.

Sadomasochism has always had its articulate evangelists, from the Marquis de Sade, the 18th-century French libertine and erotic novelist, to Kenneth Tynan, the Observer‘s illustrious theatre critic, who once argued that spanking was the path to emotional and intellectual freedom. Yet James has managed to get millions of average readers to consider the place of erotic pain in a relationship without even advancing an argument or pretending to any literary merit. The book is “my midlife crisis writ large”, Erika Leonard, the middle-aged British woman behind the pseudonym EL James, has recently admitted, adding that she put “all my fantasies in there”.

So has James created the latest commercial genre for our age – what the commentator India Knight has called “the porn version of cupcakes and Cath Kidston”? Or does her racy trilogy answer a deeper, unmet need among women readers?

The feminist writer and academic Marina Warner believes the unexpectedly wide appeal of this explicit fiction could be a sign of how difficult people now find it to feel aroused in an era when sex and nudity have become so commonplace. “There has been a general unveiling of the body in our culture and there is a connection between prohibition and arousal,” she said. “It is in some way linked to our feelings about the sacred and the profane. I definitely don’t want to go back to censorship, but I don’t think the answer is to reach for extremes either.”

Warner, like the late writer Angela Carter, has a strong interest in the power of myth and folklore. “Women should be allowed to read what they want, and to write what they want, but maybe they should not be so confident that they are not just playing a part in some larger commercial nexus.”

The nature of a myth or a fantasy always has something to say about society, she argues. “It is an effect of sexual politics and I don’t think it is neutral. In fact, I rather believe in the power of fantasy. We are driven by what we dream and by what we desire and hope for. I don’t think fantasy is hermetically sealed from the rest of our lives.”

Warner cites Carter’s provocative 1979 essay, The Sadeian Woman, as a smart approach to the politics of abusive fantasy. In it the writer suggested provocatively that de Sade merely mirrored honestly the male-dominated hierarchy of his times.

“A book like Fifty Shades of Grey can collude with the status quo, where men are still largely in charge, even though it appears to be playful,” says Warner.

Women writers have addressed extreme fantasies in the past, from Anne Desclos’s Story of O (1954), written under the name of Pauline Réage, to Fay Weldon’s The Lives and Loves of a She-Devil and The Piano Teacher, by the Austrian Nobel laureate Elfriede Jelinek. In EL James’s books the issues are handled more straightforwardly. When Christian introduces Anastasia to his “playroom” he warns her that she won’t find an Xbox or PlayStation in there.

“Producing a key from his pocket, he unlocks yet another door and takes a deep breath.

“You can leave anytime. The helicopter is on standby to take you whenever you want to go, you can stay the night and go home in the morning. It’s fine whatever you decide.”

“Just open the damn door, Christian.”

He opens the door and stands back to let me in. I gaze at him once more. I so want to know what’s in here. Taking a deep breath I walk in. And it feels like I’ve time-travelled back to the 16th century and the Spanish Inquisition.”

Internet discussions of the book on sites such as Mumsnet concentrate on distinguishing it from pornography because it is “character-driven”, which some fans feel makes it superior.

The popularity of the book has also sparked debates online about the definition of a “kinky” sexual relationship as opposed to a “vanilla” one (with vanilla defined by some as “lights-out missionary”).

Most of the Mumsnet users, even those who enjoy James’s books, are against dating men in real life who have a taste for discipline in the bedroom. One contributor does point out, however, that it might be worth considering, after all, that “dungeon full of fetish gear = owns own property”.

Joking aside, the forensic psychotherapist Estela Welldon, author of the books Mother, Madonna, Whore, theIdealization and Denigration of Motherhood, and Sadomasochism, is appalled by the mass appeal of the Grey series of books.

“It is a terrible turning back of the clock for a book like this to have such enormous success,” she declared. “It is as if women are now trying to apologise for the success they have had in a man’s world. It is a sort of response to the modern age, but a very primitive response.”

Clinically speaking, she said, she had found there was a big gap between those patients who fantasised about violence and those who had a dangerous masochistic habit, but there was a connection. “One can lead to the other, if someone cannot get it out of their system. They have so little self-regard and then they find a man who is unconsciously designed to perpetrate things they wanted to do to themselves. It is about giving up responsibility too.”

Welldon said she was ashamed that so many women were reading the trilogy, but was reluctant to give the books the status of a forbidden delight. “I would choose to minimise them, but it seems that women are identifying with them and that is bizarre.”

Tynan, in his effort to convert the public to his own taboo sexual practice, wrote a sketch called Triangle which was dropped from the London revue Carte Blanche and then planned to finance and produce an erotic film on the subject.

An admirer of de Sade, he argued darkly in his diaries that sexual fulfilment and fantasy were in complete opposition to marriage and relationships based on companionship. James, by contrast, is now quite determined to have her cake and eat it in the Grey books. Her hero Christian seems prepared to renounce all his power games and whips.

“He makes me graceful, that’s his skill. He makes me sexy, because that’s what he is. He makes me feel loved, because in spite of his fifty shades, he has a wealth of love to give,” declares Anastasia.

Whether the Grey books are porn dressed up as romance, or romance dressed up as porn, remains up for debate. Whatever the answer, it is absolutely clear that for a while there will be nothing so good for flogging books as books about flogging.